The Big Problem With US Fish

If you think the economy has taken a dive in recent years, take a gander at the closest stream running by your house. Chances are, it's not in any better shape.

The Environmental Protection Agency (EPA) has just released its assessment of America's rivers and streams, and it paints a very bleak picture: Only 21% can be considered "in good condition," down from 27% in 2004.

In 2008 and 2009, the EPA sampled water from streams and rivers in 2,000 different locations. Those samplings revealed that 40% were heavily contaminated with phosphorous and 28% with nitrogen. Both chemicals run off farms and lawns and pollute water, robbing waterways of oxygen and leading to algae blooms that kill fish and other aquatic animals. (Don't contribute to the problem in your yard. Here's how to Fertilize Your Lawn Without Poisoning the Rivers.)

The polluted streams aren't only bad for fish. In a smaller sampling of 542 rivers, the researchers collected various species of US freshwater fish, including largemouth and smallmouth bass, walleye, and various trout and catfish species, and tested those for mercury contamination. Every single fish sampled had quantifiable levels of mercury, and about 35% of the rivers from which they came contained mercury at levels higher than what is considered safe for human health. (The EPA also tested the fish for residues of selenium, pesticides, PCBs, and other contaminants, but those results haven't been released yet.)

Freshwater fish make up about half of the fish eaten in the US each year, and this is not the first study to find that US fish are contaminated with the heavy metal, which is spewed from coal-fired power plants and other industrial facilities. The US Geological Survey has also detected mercury in every freshwater fish it's tested in its annual samplings of US rivers and streams, and the EPA found that 55% of freshwater fish were contaminated in its last freshwater-fish tests in 2004.

Ultimately, this survey shows that it's not just ocean species like tuna that should be avoided because of high mercury levels. And, while the species the EPA tested—largemouth and smallmouth bass, walleye, wild trout, and catfish—often have the highest mercury levels, other regionally specific species can be contaminated as well.

What's the big deal? You've probably heard that mercury contamination can lead to lowered IQ in children, but it's also bad for adults. A recent study from Syracuse University found that mercury promotes inflammation, a precursor to heart disease, diabetes, depression, hypertension, heart attack, stroke, cancer, Alzheimer’s disease, and even dementia.

When you get a craving for truly local fish, check with your state's local department of environmental protection or fish and wildlife service to stay on top of mercury warnings. In the event that you can't find those, the EPA recommends that you eat up to 6 ounces (one serving) per week of fish that was caught from local waters and that you don't consume any other fish that week.